This mother ******

[THATpurpleKUSH 5,000+ posts]

I just read through everyones responses, mazdakid and I have the right ideas about the port. Theres not enough clearance at the hatch and the shape of the port being a thin mail slot is whats doing it, I would bet $ on it. I would have done port to the rear with an 8in round port.

With 3.5 cu/ft and a tune of 34hz you would need a length of about 27.62 with an 8inch port. You could put a V right behind it to direct the airflow and that way you could choke down the clearance at the mouth and not suffer. I used a 6in port and left 4 1/4inches of clearance for my box. I think you should do a variation of what I did here:

my box is 36w 14h 22d

 

[LosIsATool 5,000+ posts]

I didn't read through any of the other responses, but is your port seriously ~3inches wide and the width of the box (~3ft)? Thats your prob, it violates the 9:1 ratio and tuning and phasing is changing. I would not have paid for that box, esp if they changed the design without your approval.

2 inches wide

 

[RangerDangerV2 5,000+ posts]

port does seem a little thin and long... best to make it as close to a 1:1 ratio...

 

[THATpurpleKUSH 5,000+ posts]

Ok so you have a 2inch wide port thats ~34inches long? And you personally designed it?

This may damage your ego a bit, but maybe you should leave the designing to the pro's. Not trying to be a ****, but thats how I see it. Not everyone is a designer or builder. I'm by no means a pro but I have received a lot of guidance from a local shop that has a few Meca world titles and I feel that puts me a step above most others.

 

[LosIsATool 5,000+ posts]

Ok so you have a 2inch wide port thats ~34inches long? And you personally designed it?
This may damage your ego a bit, but maybe you should leave the designing to the pro's. Not trying to be a ****, but thats how I see it. Not everyone is a designer or builder. I'm by no means a pro but I have received a lot of guidance from a local shop that has a few Meca world titles and I feel that puts me a step above most others.

That's what he did. What I wanted was 1.8 deep. When he did that it took away way more internal then he thought it would. Added 3 sq inches of port per cub. It changed everything. I've seen this done in SUVs and it worked. It loads right off the hatch which is sealed up.

 

[THATpurpleKUSH 5,000+ posts]

So you wanted an even smaller port and he bumped it up by .2? That change won't cause the losses you are experiencing. Your problem is coming from the fact that your port ratio is somewhere around 17:1. The pressure is getting trapped in the sides and is causing turbulence and isn't able to escape. When you use a slot port, you want the ratio as close to 1:1 because, next to a round port, that is the most efficient design you can get. Ports are about flowing, or fluid dynamics. Even though air is a gas and not liquid, it is still included in fluid dynamics. Think about drains and pipes...how many square or rectangular drains and pipes have you ever seen? The reason you only see round pipes is because they flow the most efficient. The further you deviate from a round design when trying to flow something through it, the more inefficient it will be.

and don't anyone give that tl;dr bs for what I just wrote.

 

[LosIsATool 5,000+ posts]

So you wanted an even smaller port and he bumped it up by .2? That change won't cause the losses you are experiencing. Your problem is coming from the fact that your port ratio is somewhere around 17:1. The pressure is getting trapped in the sides and is causing turbulence and isn't able to escape. When you use a slot port, you want the ratio as close to 1:1 because, next to a round port, that is the most efficient design you can get. Ports are about flowing, or fluid dynamics. Even though air is a gas and not liquid, it is still included in fluid dynamics. Think about drains and pipes...how many square or rectangular drains and pipes have you ever seen? The reason you only see round pipes is because they flow the most efficient. The further you deviate from a round design when trying to flow something through it, the more inefficient it will be.
and don't anyone give that tl;dr bs for what I just wrote.

**** it

 

[THATpurpleKUSH 5,000+ posts]

Just tryin to help, that setup should be much closer if not past 150. I'd be salty as fuck if I was you and dropped all that $ and wasnt getting higher numbers.

 

[LosIsATool 5,000+ posts]

Just tryin to help, that setup should be much closer if not past 150. I'd be salty as fuck if I was you and dropped all that $ and wasnt getting higher numbers.

It's really musical since I put the old box back in. Everybody says a 3db difference is noticable. It's more then noticeable.

 

[JayDubb757 10+ year member]

[quote name='DCtC']I found a good one but this was paid for about a month ago. @JayDubb757 ;
Would having that much port area effect it that bad?[/QUOTE]



That's bullchit!
I would make the guy rebuild it the way it was designed. He should have talked to you prior to building about making any changes.
If he rebuilds it to your specs, and you still don't like the output, you can bring it to my job and we can modify it or salvage the mdf for your next box.

 

[wenn_du_weinst 10+ year member]

I often use rear gates/ hatches as loading walls. I how ever do not just guess at it.

 

[Trippymane 10+ year member]

I think with the port being so wide you would be better off throwing a divider in there and making it 2 smaller ports.

 

[LosIsATool 5,000+ posts]

That's bullchit! I would make the guy rebuild it the way it was designed. He should have talked to you prior to building about making any changes.

If he rebuilds it to your specs, and you still don't like the output, you can bring it to my job and we can modify it or salvage the mdf for your next box.

He just said he will build something, if it works I'll pay him.